In the power system, SF6 relay is a widely used protection and control element, whose role is to monitor the SF6 gas pressure in the confined gas chamber of high-voltage switch, GIS, etc., so as to ensure the safe operation of high-voltage switch, GIS and other electrical equipment.
For the test of SF6 relay, the state has the corresponding regulations and specifications, then we need to test the SF6 relay according to these national regulations and specifications. SF6 relays are relatively simple to test before installation. However, in more cases, we conduct field tests on SF6 relays that have been installed on electrical equipment. In view of the timeliness of power engineering, we are unlikely to be allowed to remove SF6 density relays for testing.
We need to first adjust the valve switch next to the SF6 gas density relay from the monitoring position to the closed position (different manufacturers call it differently, but the meaning is the same), and close the SF6 relay and GIS and other electrical equipment connection. If this operation is not performed, the gas cylinder configured by SF6 relay tester cannot achieve the purpose of controlling and changing the air pressure at all, so the test cannot be completed.
The connection of SF6 relay tester cannot be directly used for direct connection, because after we close the connection of SF6 relay, there is still gas with previous pressure value in SF6 density relay. If the previous gas in the SF6 relay is not discharged, the SF6 relay itself has a certain pressure, so it is not feasible for the density relay tester to control the gas to lift the pressure of the SF6 relay, and the result is that the SF6 relay does not operate. The SF6 relay adapter can be used to discharge the SF6 gas directly without any wiring.
After the above preparations are completed, subsequent tests can be performed according to all the SF6 relay testers on the market. In the process of operation, attention should be paid to the ambient temperature. In the best case, it is measured when the temperature is relatively stable. Because there is a certain relationship between air pressure and temperature, the higher the temperature accuracy, the more accurate the test results, and the determination of the pressure value at P20 temperature is more accurate.
SF6 gas relay can accurately measure the density value of SF6 gas only when the circuit breaker is out of operation and the temperature inside and outside the circuit breaker is balanced. When the circuit breaker is running, if the circuit breaker leaks SF6 gas, due to the effect of temperature rise, it is necessary to leak more SF6 gas than when the circuit breaker is out of operation, so that the electrical contact of the density relay can be closed. In terms of calibration of SF6 circuit breaker density meter or density relay, it is the use of instruments to automatically convert the SF6 gas pressure value at 20 ℃, showing the density value at various temperatures and pressures, and the use of instruments to simulate a variety of pressure for comparison, in order to observe the contact of the electrical contacts, and observe whether it can send signal or close the circuit breaker within the specified value of low pressure, so as to determine the quality of density meter or density relay of SF6 circuit breaker.